Excellent, Ben! I have enough fiberglass cloth for at least a couple layers.
________________________________
From: Ben Hallert <EMAIL HIDDEN>
To: Laura Harris <EMAIL HIDDEN>
Cc: Thomas A Ramsey <EMAIL HIDDEN>; "EMAIL HIDDEN" <EMAIL HIDDEN>
Sent: Tuesday, November 1, 2011 9:13 AM
Subject: Re: [Discuss] Near-space balloon: Foam ball located and purchased
I have epoxy we can use plus microballoons. For anyone who is
unfamiliar with microballoons, they're a super fine fiberglass dust
that you can mix with epoxy resin that's ideal for 'filler' projects
like this. The epoxy doesn't really add significant strength on its
own, so having a material (like microballoons) helps a lot. Mixed
with the resin, you can then 'smear' it onto the polystyrene.
So:
Cuts weight
+
Increases strength.
=
#winning.
- Ben
On Tue, Nov 1, 2011 at 9:01 AM, Laura Harris <EMAIL HIDDEN> wrote:
> Thanks for all the input, everyone. Ben and I will go over the various
> approaches and make some design decisions.
>> We'll need a pair of simple cradles to hold the halves on the workbench
> during construction and assembly- these can be as simple as a pair of sturdy
> cardboard boxes with 8" dia holes cut in one side, and edging the openings
> of the holes with something cushy like thin craft foam. If someone wants to
> fab those up and have them at the shop no later than next Sunday, that would
> be great. Otherwise, we'll throw something together on Sunday. I expect the
> ball to arrive in the next couple days so construction will be able to start
> this next weekend.
>> I'll build a little enclosure to test the impact that gold mylar has on GPS
> performance- will have it at the shop next Sunday.
> Does anyone have any epoxy resin- not the glue, but the stuff used for
> fiberglassing? West Systems 105 is the material of choice but it's spendy-
> $45 for a quart of resin and the fast hardener + whatever shipping costs.
>>> L
>> ________________________________
> From: Thomas A Ramsey <EMAIL HIDDEN>
> To: EMAIL HIDDEN> Sent: Monday, October 31, 2011 7:11 PM
> Subject: Re: [Discuss] Near-space balloon: Foam ball located and purchased
>> I'm liking the nylon all-thread idea but I am a little concerned with it's
> strength. If we only have the one all-thread and it breaks our strips we
> lose the bottom half on the rig. I also don't trust velcro AT ALL. If it
> becomes wet or consistently stressed it will disconnect. Zip ties are great
> but difficult to reuse (they can in fact be reused). If we decide against
> zip ties I propose using multiple all-threads. Perhaps three or four; one
> down the center then the others at 45 degrees from the top center straight
> (nearly so to avoid each other) through. Nylon to keep weight down. I know
> it may make for more supports to work around but we should be able to handle
> it.
>> I really like the strobe ideas as well. If we do have a separate strobe rig
> I think it may need to be insulated as well. I've read temperatures as low
> as -60 to -70 Celsius at the altitude we expect to go and most consumer
> grade electronics like leds are only rated about -20.
>> -Tom
>> On Mon, 31 Oct 2011 14:35:59 -0700 (PDT), Laura Harris wrote:
>> We can use nylon all-thread for the central support rod, if we go that
>> route. Long velcro-enabled straps would be reusable and strong though
>> a bit heavier that zipties (but not by much). If we used a net, we'd
>> still want to secure the halves together (unless you were thinking of
>> drawing the net up into a tight neck at the top . . .). I'm leaning
>> towards the nylon all thread center support rod approach, personally.
>>>> As for the interior construction, the interior walls, floors, and
>> ribbing are 5mm foam-core. I was thinking of using gold mylar film for
>> the reflective insulation, but we can go without it and fill dead
>> areas with extra foam.
>>>> Reasoning behind a partial hard-shell was assuming the ball will land
>> bottom down so a full shell could be avoided to save weight. Still, it
>> would definitely make it a tougher rig- more likely to survive for
>> reuse. I was thinking of using fiberglass with epoxy resin for the
>> hard shell.
>>>> Idea for paint scheme: paint the bottom 3rd black and the rest red.
>> Black so it is easier to see on the way up (against the sky) and red
>> so it stands out on the ground. Also, a fluorescent colored parachute.
>>>>>> We can use 1-watt LEDs for strobes. With the short duty cycle a strobe
>> requires, we won't need heat-sinks for the LEDs and they are bright
>> enough to be easily seen in daylight. A simple 555 timer driving a FET
>> switch is all we'd need for a driver. Another thing we can do is hang
>> a strobe from the tether. That way its weight is not considered part
>> of the 6lb payload limit (if I understand the FAA regs correctly). One
>> of those little waterproof xenon strobes doesn't weigh much, either.
>>>> -------------------------
>> FROM: Rick Osgood
>> TO: Laura Harris
>> CC: Ben Hallert ; "EMAIL HIDDEN"
>> SENT: Monday, October 31, 2011 1:58 PM
>> SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
>> purchased
>>>> I just had another thought about the design of the chassis that we
>> didn't bring up at our meeting yesterday. We need to be careful about
>> the material the payload is made of as well as the GPS placement. The
>> eTrex doesn't have an external antenna so we need to make sure it can
>> get an accurate GPS lock from inside the payload. So any metal above
>> it would be a bad idea. So the chassis needs to be insulated but with
>> material that the GPS radio signals can get through.
>>>> On Mon, Oct 31, 2011 at 1:51 PM, Rick Osgood wrote:
>>>>> Ben, so your idea would be to have the cord come through the sphere
>>> via a hole in the top and then attach to the inside of the bottom
>>> half? I want to make sure I understand your idea correctly. That
>>> sounds like it could definitely work and I like that it would remove
>>> the requirement for extra reinforcement on the top half. Only
>>> downside would be having the rope going through the payload where it
>>> could get in the way of the electronics.
>>>>>> Laura, I think the zip ties idea could be cheap, simple, and
>>> effective. It would be nice to have something that didn't require
>>> cutting and replacing the zip ties every time we open and close it
>>> though.
>>>>>> The last balloon I did, we just had a threaded rod going all the way
>>> through the center of the payload vertically. There was a washer and
>>> a nut on each side to hold the two pieces tightly together. Then a
>>> small horizontal hole was drilled through the threaded rod at the
>>> top so we could stick a sort of hook through it where the line was
>>> attached. The threaded rod was nice and strong but it will add more
>>> weight and then you have a metal rod going all the way through the
>>> center of the payload which can make the inside electronics layout
>>> more difficult. You can see it in some of the photos from this site:
>>>http://www.toddfun.com/2011/02/20/high-altitude-balloon-launch-2/>>> [17] . Here is one example photo:
>>>>>> On Mon, Oct 31, 2011 at 1:29 PM, Laura Harris wrote:
>>>>>>> Ohh- that looks good, Ben.
>>>>>>>> One idea for holding the halves together is to use a pair of
>>>> extra-long nylon zip ties running longitudinally at 90 degrees to
>>>> each other- grooves formed in the surface would keep them from
>>>> sliding off. They're strong and light and they avoid the need for
>>>> any hardware.
>>>>>>>> -------------------------
>>>> FROM: Ben Hallert
>>>> TO: Laura Harris
>>>> CC: Rick Osgood ;
>>>> "EMAIL HIDDEN [4]"
>>>> SENT: Monday, October 31, 2011 1:12 PM
>>>>>>>> SUBJECT: Re: [Discuss] Near-space balloon: Foam ball located and
>>>> purchased
>>>>>>>> May I suggest that instead of attaching the cord to the top, we
>>>> run it
>>>> down and attach it to where the battery bay is? This way the whole
>>>> thing is 'sitting' on the cord and we can cut any weight created
>>>> by
>>>> reinforcements that would reach to the top of the sphere. Namely,
>>>> the
>>>> only 'strength' needed would be at the bottom where it's already
>>>> planned to exist. This also reduces risk of retrieving just the
>>>> top
>>>> of the sphere. :) I've attached a modified version of the
>>>> drawing.
>>>>>>>> - Ben
>>>>>>>> On Mon, Oct 31, 2011 at 12:51 P.M, Laura Harris wrote:
>>>> > The ball comes split in half so it's just a matter of holding
>>>> it together in
>>>>> flight. I've attached a pic of a sketch showing a preliminary
>>>> idea for
>>>>> construction.
>>>>>>>>>> ________________________________
>>>> > From: Rick Osgood
>>>>> To: Laura Harris
>>>>> Cc: "EMAIL HIDDEN [9]"
>>>> >
>>>>> Sent: Monday, October 31, 2011 10:54 AM
>>>>> Subject: Re: [Discuss] Near-space balloon: Foam ball located and
>>>> purchased
>>>> >
>>>>> Sweet! Do you plan to mold something around the sphere? I'm
>>>> curious to see
>>>>> your final design and how we will be able to open it up and
>>>> mount
>>>>> everything.
>>>>>>>>>> On Mon, Oct 31, 2011 at 9:53 AM, Laura Harris wrote:
>>>>>>>>>> I found a 12" dia hollow polystyrene foam ball and purchased
>>>> one. Should be
>>>> > here in a few days. This is it:
>>>>>http://www.plasteelcorp.com/mm5/merchant.mvc [12]?
>>>>> This dramatically accelerates the build progress. :)
>>>> > L
>>>>>>>>>>>>>>> _______________________________________________
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